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Skyrmions as well as skyrmion bags in magnetic thin films are promising candidates for future high-density memory devices. The observation of skyrmion bags in liquid crystals and their predicted existence in ferromagnetic films has sparked theoretical studies on current induced dynamics of these topological charges. Here using micromagnetism, we study the impact of out of plane strain on the stability of skyrmion and skyrmion bags in ferromagnetic thin film. We further studied the current induced dynamics in the presence of out of plane strain gradient. We demonstrate that out of plane strain gradient direction with respect to the electron flow can be an efficient way to control the dynamics of topological charges. Specifically, the deflection of skyrmion bags correlates with their topological degree, and an appropriate strain gradient can counteract skyrmion Hall effects, enabling straight-line movement. Our micromagnetic simulations align well with theoretical predictions from the Thiele equation.

Magnetic nanotubes have garnered immense attention for their potential in high-density magnetic memory, owing to their stable flux closure configuration and fast, reproducible reversal processes. However, characterizing their magnetic configuration through straightforward methodologies remains a challenge in both scope and detail. Here, we elucidate the magnetic state details using Remanence Field Ferromagnetic Resonance Spectroscopy (RFMR) for arrays of electrodeposited nanotubes. Micromagnetic simulations revealed distinct spin configurations while coming from saturation, including the edge vortex, onion, uniform and curling states, with chirality variations depending on the preparation field direction. Dynamic measurements, coupled with RFMR spectra analysis, unveiled multiple FMR modes corresponding to these spin configurations. The evolution of spin configurations under bias fields were studied, indicating nucleation within the curling state. Observations revealed opposite RFMR spectra, denoting opposite magnetic spin configurations after removing the positive and negative saturating fields when the magnetic field was applied along {theta_H=0} and perpendicular {theta_H= 90} to the nanotube axis. We observed a mixture of the non-uniform curling states with the end vortex state (onion-like curling state) at the end of the nanotubes for the theta_H=0(90) and uniform magnetization states in the middle of the nanotubes for the theta_H=0 configuration. Building on RFMR information, frequency-swept FMR absorption spectra obtained at different bias fields allowed the characterization of magnetization states. This picture was supported by micromagnetic simulations. These findings were further substantiated with First Order Reversal Curve measurements (FORC).

Spin-orbit torque (SOT)-based perpendicularly magnetized memory devices with multistate memory have garnered significant interest due to their applicability in low-power in-memory analog computing. However, current methods are hindered by initialization problems such as prolonged writing duration, and limitations on the number of magnetic states. Consequently, a universal method for achieving multistate in PMA-based stacks remains elusive. Here, we propose a general experimental method for achieving multistate without any initialization step in SOT-driven magnetization switching by integrating an external out-of-plane magnetic field. Motivated by macrospin calculations coupled with micromagnetic simulations, which demonstrate the plausibility of magnetization state changes due to out-of-plane field integration, we experimentally verify multistate behavior in Pt/Co/Pt and W/Pt/Co/AlOx stacks. The occurrence of multistate behavior is attributed to intermediate domain states with N\'eel domain walls. We achieve repeatable 18 multistate configurations with a minimal reduction in retentivity through energy barrier measurements, paving the way for efficient analog computing.